CN110261445B - In-situ growth nanometer In based on non-metallic mineral electrode substrate surface2O3Room temperature NO of2Sensor and preparation method - Google Patents

Abstract

The invention discloses a non-metal mineral electrode-based In-situ growth method for nanometer In on the surface of a substrate₂O₃Room temperature NO of₂A sensor and a preparation method thereof belong to the field of gas sensors made of metal oxide semiconductor materials. The invention takes a non-metallic mineral porous ceramic electrode as a substrate, adopts a direct current sputtering method to sputter an interdigital electrode on the surface of the substrate, and adopts a hydrothermal method to grow In situ on the surface of the interdigital electrode₂O₃Nano material, said In₂O₃The nano material is In a rod-shaped structure, is uniformly and densely distributed on the surface of the substrate, has the diameter of 120-200 nm and the length of 0.5-1 mu m, and is formed by mutually stacking nano particles In₂O₃A cubic phase crystal structure with a diameter of 10-30 nm. The gas sensor can be used for detecting 0.1-1 ppm NO under the working condition of room temperature and under the auxiliary recovery of UV light₂Has rapid response and recovery speed, excellent selectivity and long-term stability, and good application prospect.

Description

In-situ growth nanometer In based on non-metallic mineral electrode substrate surface2O3Room temperature NO of2Sensor and preparation method

Technical Field

The invention belongs to the technical field of gas sensors made of metal oxide semiconductor materials, and particularly relates to nano In with room-temperature gas-sensitive response characteristic₂O₃A gas sensor and a preparation method thereof, In particular to a non-metallic mineral electrode-based In-situ growth nanometer In on the surface of a substrate₂O₃Room temperature NO of₂A sensor and a preparation method.

Background

Nitrogen dioxide (NO)₂) Is automobile exhaust gas andthe toxic irritant gases emitted during industrial processes are one of the main pollutants responsible for acid rain and photochemical smog formation, even 1ppm NO₂It is also very harmful to human body, and therefore, it is effective for low concentration of NO₂The detection of (2) is extremely necessary. The metal oxide semiconductor gas sensor has been widely used for detecting toxic and harmful gases due to its characteristics of high sensitivity, online real-time monitoring, miniaturization, easy integration, strong portability and the like. At present, based on WO₃、SnO₂ZnO and In₂O₃The gas sensor of the metal oxide nano material can be used for low-concentration NO₂Has good gas-sensitive property, but the working temperature of the gas-sensitive material is required to be generally 100-400 ℃. The long-term high-temperature work can not only increase the energy consumption, but also promote the secondary growth or agglomeration of the nano-crystalline grains to change the appearance of the nano-crystalline grains, so that the service life of the gas sensor is shortened. In addition, the high operating temperature also easily ignites flammable and explosive gases, thereby limiting the application range of such gas sensors.

Therefore, NO under room temperature operating conditions in recent years₂The sensor is always a hotspot and a difficulty in the field of gas-sensitive research. Currently, researchers have attempted to adopt effective methods to reduce the working temperature of a gas sensor to room temperature, including methods of nanomaterial morphology control, surface modification, noble metal doping, graphene compositing, or UV assistance. However, for most of the room temperature NO reported so far₂For gas-sensitive materials, the disadvantages of complex synthesis process, high cost, too long response/recovery time, even incomplete recovery, etc. still exist generally. Therefore, there is a need to develop NO that can operate at room temperature with a fast response/recovery rate₂A sensor. In order to overcome the disadvantage of slow or no room temperature recovery, thermal pulses or UV radiation are usually used. However, the recovery by thermal pulse desorption of gas tends to have an irreversible effect on the material, which can have an effect on the long-term stability of the gas sensor; the UV radiation nano material surface can enable gas ions and water molecules on the surface of the gas sensor to be rapidly desorbed, so that clean nano material is generatedAnd the resistance of the gas sensor is quickly restored to the initial value on the surface, so that the gas sensor is favorable for long-term circulating operation and the stability of the gas sensor is improved.

In₂O₃As a wide-band-gap semiconductor material (the band gap of the material is 3.6eV at room temperature), the material is a very promising gas-sensitive material, and can be used for low-concentration NO₂And good gas-sensitive characteristics are shown. Thus, In of various morphologies₂O₃Nano gas-sensitive materials are successfully synthesized, such as rods, wires, spheres, blocks, flowers and layered porous structures. At present, most of them are based on In₂O₃The gas sensor made of the nano material adopts a mode of firstly synthesizing the gas sensitive material and then coating the gas sensitive material on the surface of a gas sensitive electrode element to prepare the gas sensor, and the process has the defect that the ordered deposition of the material cannot be controlled, so that the appearance of the gas sensor is changed, and the long-term stability of the gas sensor is influenced. In addition, poor contact between the prepared gas-sensitive material and an electrode also leads to poor reproducibility.

Disclosure of Invention

For the current In₂O₃The gas sensor has the defects of relatively complex and single preparation method and low-concentration NO under the condition of room temperature₂The invention provides a porous ceramic electrode-based In-situ growth method for nano In₂O₃NO of₂The sensor and the preparation method thereof can achieve the effect of rapid recovery by radiating the surface of the gas sensitive material through the UV ultraviolet lamp in the recovery stage of the gas sensor.

The power of the UV ultraviolet lamp is 6W, the wavelength is 365nm, and the distance between a light source and a sample is 40 mm.

In-situ growth nanometer In based on non-metallic mineral porous ceramic electrode substrate surface₂O₃Room temperature NO of₂The sensor, the non-metal mineral electrode substrate is a non-metal mineral porous ceramic electrode substrate, and the NO is₂The sensor is In-situ grown on the surface of a non-metal mineral porous ceramic electrode substrate₂O₃Obtaining a nano material; wherein, said In₂O₃Nano materialThe nano-particles are in a rod-shaped structure and uniformly and densely grow on the surface of the electrode substrate, and the rod-shaped structure is formed by mutually stacking the nano-particles; the nano-particles are In₂O₃A cubic phase crystal structure; the rod-shaped structure has a diameter of 120-200 nm, a length of 0.5-1 μm, and the diameter of the nano-particles is 10-30 nm.

Preferably, the non-metal mineral porous ceramic electrode substrate is made of diatomite or kaolin containing aluminosilicate components, and is subjected to porous treatment by adopting a pore-forming agent pore-forming method, wherein the pore-forming agent is spherical graphite or PMMA microspheres, the average diameter of the pore-forming agent is 10-70 mu m, the addition proportion is 15-50 wt.%, and the non-metal mineral porous ceramic electrode substrate is formed by adopting a mould pressing sintering method, and the sintering temperature is 1000-1200 ℃.

Preferably, the length of the non-metal mineral porous ceramic electrode substrate is 15-20 mm, the width is 5-10 mm, and the thickness is 1-2 mm.

Furthermore, the invention also provides In-situ growth of nano In on the surface of the non-metallic mineral porous ceramic electrode substrate₂O₃Room temperature NO of₂The preparation method of the sensor comprises the following process steps:

①, taking a non-metallic mineral porous ceramic electrode as a substrate, sputtering a layer of Ni film with the thickness of 10-20 nm on the surface of the electrode substrate covering the interdigital electrode mask plate by a plasma sputtering instrument through a direct current sputtering method, and then sputtering a layer of Au film with the thickness of 50-100 nm;

② mixing InCl₃·4H₂Dissolving O in deionized water, stirring uniformly at room temperature, then adding 0.1-0.5 mL of oleic acid, stirring uniformly at room temperature, then adding urea, stirring for 5-15 min, and then transferring the mixed solution to a polytetrafluoroethylene reaction kettle, wherein InCl is₃·4H₂O concentration of 0.03-0.04 mol/L, In³⁺The molar ratio of the ions to the urea is 1: 8-1: 12;

③, vertically placing the non-metallic mineral porous ceramic electrode substrate obtained in the step ① in a polytetrafluoroethylene reaction kettle, sealing the reaction kettle, placing the reaction kettle in a box-type resistance furnace for heat treatment, heating to 60-100 ℃ at a speed of 10 ℃/min, and preserving heat for 6-14 hours;

④ after the reaction, taking out the electrode substrate, washing the electrode substrate with deionized water, drying at 80 ℃ for 1h, placing the electrode substrate In a tubular resistance furnace, heating to 300-500 ℃ at a speed of 2 ℃/min, keeping the temperature for 1-2 h, naturally cooling to room temperature, taking out the electrode substrate, placing the electrode substrate In a gas-sensitive test system, and contacting a test probe with the interdigital electrode to obtain the In₂O₃Room temperature NO with nano material as sensitive layer₂A gas sensor.

Further, in the above technical solution, the width of the fingers of the finger electrode mask plate in the step ① is 0.2-0.5 mm, and the distance between the fingers is 0.2-0.5 mm.

The invention has the beneficial effects that:

in-situ growth of In on the surface of a non-metal mineral porous ceramic electrode substrate₂O₃Nanorod arrays, and as a gas sensitive coating for gas sensors. The porous ceramic substrate can replace the high-cost high-purity silicon source or aluminum source substrate, and the porosity of the porous ceramic substrate is favorable for In the hydrothermal process₂O₃The heterogeneous nucleation of the nano material increases the nucleation sites, thereby improving the density of the product. The density of the product is increased, the growth direction of the product tends to be consistent due to the space crowding effect, so that a compact nanorod array is formed, and In is formed₂O₃The nano rod has high specific surface area due to the mesoporous structure and provides a large number of reactive sites, so that the nano rod can treat low-concentration NO at room temperature₂Has good response characteristics. By setting up the UV illumination, a fast recovery of the gas sensor can be achieved while maintaining excellent long-term stability and selectivity. In addition, the synthesis process is simple, the hydrothermal temperature is lower than 100 ℃, and the production cost of the material can be effectively reduced.

Drawings

FIG. 1 is a schematic structural view of a non-metallic mineral porous ceramic electrode substrate used in examples 1 to 3 of the present invention;

FIG. 2 is an X-ray diffraction pattern of the product prepared in example 1 of the present invention;

FIG. 3(3-1) is a view showing a surface In of a porous ceramic substrate In example 1 of the present invention₂O₃A low-magnification scanning electron microscope photograph of the product, (3-2) a medium-magnification scanning electron microscope photograph of the product, (3-3) a high-magnification scanning electron microscope photograph of the product, the upper right corner of which is a further enlarged scanning electron microscope photograph, and (3-4) a side view angle scanning electron microscope photograph of the porous ceramic substrate;

FIG. 4(4-1) is a low-power TEM photograph of a single nanorod in example 1 of the present invention, wherein the upper right corner of the low-power TEM photograph is the selected area electron diffraction pattern of the square frame portion of the nanorod; (4-2) is a high-resolution transmission electron microscope photograph, (4-3) is a high-magnification transmission electron microscope photograph, and (4-4) is a point electron energy spectrum at the circle in (4-3);

FIG. 5(5-1) is a high-resolution X-ray photoelectron spectrum of In element In the product produced In example 1 of the present invention; (5-2) is a high-resolution X-ray photoelectron spectrum of O element;

FIG. 6(6-1) is a graph showing the results of measurement of 800ppb of NO at room temperature of 25 ℃ for the gas sensor prepared in example 1 of the present invention₂Response-recovery graph of (a); (6-2) gas sensor for 800ppb NO at room temperature 25 ℃₂Response-recovery graph of (a);

FIG. 7(7-1) is a graph showing the results of the gas sensor prepared in example 1 of the present invention for various concentrations of NO at room temperature of 25 deg.C₂The dynamic response-recovery graph of (a); (7-2) sensitivity of gas sensor at room temperature of 25 ℃ and NO₂A graph of the relationship between concentrations;

FIG. 8(8-1) is a graph showing the results of measurement of 800ppb of NO at room temperature of 25 ℃ for the gas sensor prepared in example 1 of the present invention₂7 cycle response-recovery plot of (8-2) gas sensor at 25 deg.C at room temperature for 800ppb NO₂A graph of sensitivity versus number of days tested;

FIG. 9 is a graph showing the sensitivity of the gas sensor prepared in example 1 of the present invention to different gases to be detected at room temperature of 25 ℃.

Detailed Description

The following non-limiting examples are presented to enable those of ordinary skill in the art to more fully understand the present invention and are not intended to limit the invention in any way.

The test methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials are commercially available, unless otherwise specified.

Example 1

The structure diagram of the porous ceramic electrode substrate based on the nonmetallic mineral material is shown in figure 1. The electrode on the surface of the substrate is formed by respectively and sequentially sputtering Ni films and Au films on a porous ceramic substrate covered with an interdigital electrode mask plate by a direct current sputtering method, wherein the thickness of the Ni film is 10nm, the thickness of the Au film is 50nm, the width of an interdigital is 0.5mm, and the distance between the interdigital is 0.5 mm.

The specific sputtering step is to sputter a layer of Ni film firstly, the sputtering current is 17mA, and the sputtering time is 120 s; then sputtering an Au film, wherein the sputtering current is 10mA, and the sputtering time is 230 s; wherein, the sputtering environmental conditions are as follows: argon flow of 200sccm, vacuum degree of 90mTorr, and plasma sputtering apparatus (Hefeiki crystal materials technology Co., Ltd., VTC-16-3 HD).

In the above steps, the porous ceramic electrode substrate is made of kaolin, and the porousness treatment method adopts a pore-forming method using a pore-forming agent, wherein the pore-forming agent is PMMA microspheres with an average diameter of 30 μm and an addition ratio of 25 wt.%; the forming method adopts a mould pressing sintering method, and the sintering temperature is 1200 ℃.

The sintering system of the porous ceramic electrode substrate is as follows: sintering by adopting a gradient heating method, wherein a sintering system is heated from room temperature to 250 ℃ at a speed of 5 ℃/min, and the temperature is kept for 60 min; heating to 450 deg.C at a rate of 1 deg.C/min, and maintaining for 60 min; heating to 1200 deg.C at a rate of 10 deg.C/min, and maintaining for 90 min; finally, the temperature is reduced to the room temperature at 5 ℃/min.

The porous ceramic electrode substrate is 20mm long, 10mm wide and 2mm thick.

In-situ growth nanometer In based on porous ceramic electrode substrate₂O₃NO of₂A method of making a sensor, the method comprising:

① sputtering a Ni film with a thickness of 10nm and an Au film with a thickness of 50nm on the surface of the substrate covering the interdigital electrode mask plate by a plasma sputtering instrument by using a non-metallic mineral material porous ceramic electrode as the substrate through a direct current sputtering method;

② 0.35g of InCl₃·4H₂Dissolving O in 36mL of deionized water, and stirring at room temperature for 10 min; then adding 0.25mL of oleic acid, and stirring for 10min at room temperature; then adding 1g of urea, stirring for 10min, and finally pouring the mixed solution into a 100mL polytetrafluoroethylene reaction kettle;

③ vertically placing the non-metallic mineral porous ceramic electrode substrate obtained in step ① in a polytetrafluoroethylene reaction kettle, sealing, placing in a box-type resistance furnace for heat treatment, heating to 80 ℃ at a speed of 10 ℃/min, and keeping the temperature for 12 h;

④ after the reaction, taking out the electrode substrate, washing the electrode substrate with deionized water, drying at 80 deg.C for 1h, placing In a tubular resistance furnace, heating to 400 deg.C at 2 deg.C/min, maintaining the temperature for 1h, naturally cooling to room temperature, taking out the electrode substrate, placing In a gas sensitive test system, contacting the test probe with the interdigital electrode to obtain In₂O₃Room temperature NO with nano material as sensitive layer₂A gas sensor.

The gas sensitive test method was carried out using (GB-T15653-1995).

The XRD pattern of the product obtained by hydrothermal synthesis on the surface of the porous ceramic substrate is shown in FIG. 2. As can be seen from FIG. 2, the diffraction peaks of the products can both correspond to In of the cubic phase crystal structure₂O₃(JCPDS number 88-2160), no other impurity peaks appear, and the product has good crystallinity and high purity. FIG. 3-1 and FIG. 3-2 show In the porous ceramic pore structure surface₂O₃The low-magnification and medium-magnification scanning electron microscope photos of the product show that a large amount of the product is uniformly and densely distributed in the inner part and the outer part of the pore structure. 3-3 is a high magnification scanning electron micrograph of the product, which shows that the product has a rod-like structure and a diameter of 120-200 nm; as can be seen from the enlarged photograph of the upper right corner, the rod-shaped structure has a rough surface and is formed by stacking a large number of nanoparticlesThe diameter is 10-30 nm. FIG. 3-4 is a scanning electron microscope photograph of the side view of the product, which shows that the diameter of the nanorods is 0.5-1 μm, and the nanorods are tightly connected to the substrate. FIG. 4-1 is a low-power TEM photograph of a single nanorod in the product, where it can be seen that the nanorod has a diameter of 170nm and a surface composed of a large number of nanoparticles, which is consistent with the result of the SEM photograph; the upper right corner of the nano rod is a selected area electron diffraction pattern of the square frame part of the nano rod, which proves that the nano rod has a polycrystalline structure. FIG. 4-2 is a high resolution TEM photograph of the single nanorod with lattice spacing and cubic crystal In₂O₃The structures are matched, and the crystal structures are further proved. 4-3 is a high-magnification transmission electron microscope photograph, and it can be seen that the diameter of the nano-particles constituting the nanorods is about 10nm, which is consistent with the scanning electron microscope results. FIG. 4-4 is a dot electron energy spectrum of the circle In FIG. 4-3, and it can be seen that the nanorod is composed of In and O elements, wherein the peaks of Cu and C elements are from the detection device. FIG. 5-1 is a high-resolution X-ray photoelectron spectrum of In element In the obtained product, In which peaks at 441.16eV and 451.76eV correspond to 3d of In element, respectively_5/2And 3d_3/2Spin orbit peak, indicating that In the sample is In³⁺. FIG. 5-2 is a high-resolution X-ray photoelectron spectrum of the O element In the obtained product, In which peaks at 529.66eV and 531.31eV respectively correspond to In₂O₃Lattice oxygen (O) of nanowires_Ⅰ) And surface adsorption of oxygen (O)_Ⅱ) Wherein the content of the surface adsorbed oxygen directly influences the gas-sensitive performance of the material.

FIG. 6-1 is a graph showing the measured gas concentration at 25 ℃ for 800ppb NO in the gas sensor prepared₂Response-recovery graph of (a). As can be seen from the figure, when 800ppb NO is introduced₂Then, the resistance of the gas sensor rapidly rises and tends to be stable, the sensitivity value is 14.9, and the response time is 14 s; when discharging NO₂Thereafter, the resistance of the gas sensor fails to return quickly to the initial value. However, when the surface of the gas sensor is irradiated with UV light, it can be seen from FIG. 6-2 that the resistance of the gas sensor can be rapidly restored to the initial value with a restoration time of 32s, indicating that the gas sensor is used for a long timeExhibit good response-recovery characteristics with the aid of UV light. FIG. 7-1 shows the measurement of NO at 0.1 to 1ppm at room temperature of 25 ℃ in the gas sensor₂Dynamic response-recovery graph of (a). It can be seen from the figure that the resistance of the gas sensor changes with NO₂The increase in concentration shows a tendency to increase, with a corresponding sensitivity to NO₂The relationship between the concentrations is shown in FIG. 7-2 for 100, 200, 400, 600, 800 and 1000ppb NO₂Are 1.4, 1.6, 3.8, 8.4, 14.9 and 20.8, respectively. FIG. 8-1 is a graph showing that the gas sensor is sensitive to 800ppb NO at room temperature of 25 deg.C₂The 7-time cycle response-recovery curve chart shows that the characteristics of the dynamic response-recovery curve are basically the same; from FIG. 8-2 the gas sensor is sensitive to 800ppb NO at 25 ℃ of room temperature₂The sensitivity value fluctuation is small, which shows that the gas sensor has good repeatability and long-term stability. FIG. 9 is a graph showing the sensitivity of the gas sensor to different gases to be detected at room temperature of 25 deg.C, from which it can be seen that the gas sensor is sensitive to 1ppm NO₂The sensitivity is highest, the sensitivity value is 20.8, which is obviously higher than 1000ppm H₂And 100ppm of other gases, indicating NO at room temperature₂Has excellent gas selectivity.

Example 2

The structure diagram of the porous ceramic electrode substrate based on the nonmetallic mineral material is shown in figure 1. The electrode on the surface of the substrate is formed by respectively and sequentially sputtering Ni films and Au films on a porous ceramic substrate covered with an interdigital electrode mask plate by a direct current sputtering method, wherein the thickness of the Ni film is 10nm, the thickness of the Au film is 50nm, the width of an interdigital is 0.5mm, and the distance between the interdigital is 0.5 mm.

The specific sputtering step is to sputter a layer of Ni film firstly, the sputtering current is 17mA, and the sputtering time is 120 s; then sputtering an Au film, wherein the sputtering current is 10mA, and the sputtering time is 230 s; wherein, the sputtering environmental conditions are as follows: the flow rate of argon gas was 200sccm, the degree of vacuum was 90mTorr, and a plasma sputter (Vitaceae Crystal Material technology Co., Ltd., VTC-16-3HD) was used for sputtering.

The porous ceramic electrode substrate in the above steps is made of diatomite, and the porous treatment method adopts a pore-forming agent pore-forming method, wherein the pore-forming agent is PMMA microspheres with an average diameter of 50 μm and an addition ratio of 15 wt.%; the forming method adopts a mould pressing sintering method, and the sintering temperature is 1000 ℃.

The sintering system of the porous ceramic electrode substrate is as follows: sintering by adopting a gradient heating method, wherein a sintering system is heated from room temperature to 250 ℃ at a speed of 5 ℃/min, and the temperature is kept for 60 min; heating to 450 deg.C at a rate of 1 deg.C/min, and maintaining for 60 min; then heating to 1000 ℃ at a speed of 10 ℃/min, and preserving heat for 180 min; finally, the temperature is reduced to the room temperature at 5 ℃/min.

The porous ceramic electrode substrate is 20mm long, 10mm wide and 2mm thick.

In-situ growth nanometer In based on porous ceramic electrode substrate₂O₃NO of₂A method of making a sensor, the method comprising:

① sputtering a Ni film with a thickness of 10nm and an Au film with a thickness of 50nm on the surface of the substrate covering the interdigital electrode mask plate by a plasma sputtering instrument by using a non-metallic mineral material porous ceramic electrode as the substrate through a direct current sputtering method;

② 0.35g of InCl₃·4H₂Dissolving O in 36mL of deionized water, and stirring at room temperature for 10 min; then adding 0.25mL of oleic acid, and stirring for 10min at room temperature; then adding 1g of urea, stirring for 10min, and finally pouring the mixed solution into a 100mL polytetrafluoroethylene reaction kettle;

③ vertically placing the non-metallic mineral porous ceramic electrode substrate obtained in step ① in a polytetrafluoroethylene reaction kettle, sealing, placing in a box-type resistance furnace for heat treatment, heating to 80 ℃ at a speed of 10 ℃/min, and keeping the temperature for 12 h;

④ after the reaction, taking out the electrode substrate, washing the electrode substrate with deionized water, drying at 80 deg.C for 1h, placing In a tubular resistance furnace, heating to 400 deg.C at 2 deg.C/min, maintaining the temperature for 1h, naturally cooling to room temperature, taking out the electrode substrate, placing In a gas sensitive test system, contacting the test probe with the interdigital electrode to obtain In₂O₃Room temperature NO with nano material as sensitive layer₂A gas sensor.

The gas sensitive test method was carried out using (GB-T15653-1995).

Upon examination, In-based films prepared In this example₂O₃The gas sensor of the nano material is used for detecting 0.1-1 ppm NO at the room temperature of 25 DEG C₂Has good gas-sensitive property.

Example 3

The structure diagram of the porous ceramic electrode substrate based on the nonmetallic mineral material is shown in figure 1. The electrodes on the surface of the substrate are formed by respectively and sequentially sputtering Ni films and Au films on the porous ceramic substrate covered with the interdigital electrode mask plate by a direct current sputtering method, wherein the thickness of the Ni film is 10nm, the thickness of the Au film is 50nm, the width of an interdigital is 0.5mm, and the distance between the interdigital is 0.5 mm.

The specific sputtering step is to sputter a layer of Ni film firstly, the sputtering current is 17mA, and the sputtering time is 120 s; then sputtering an Au film, wherein the sputtering current is 10mA, and the sputtering time is 230 s; wherein, the sputtering environmental conditions are as follows: the flow rate of argon gas was 200sccm, the degree of vacuum was 90mTorr, and a plasma sputter (Vitaceae Crystal Material technology Co., Ltd., VTC-16-3HD) was used for sputtering.

The porous ceramic electrode substrate in the above steps is made of diatomite, and the porousness treatment method adopts a pore-forming agent pore-forming method, wherein the pore-forming agent is spherical graphite, the average diameter is 24 μm, and the addition ratio is 40 wt.%; the forming method adopts a mould pressing sintering method, and the sintering temperature is 1000 ℃.

The sintering system of the porous ceramic electrode substrate is as follows: sintering by gradient heating method, heating from room temperature to 500 deg.C at 10 deg.C/min, and maintaining for 30 min; then heating to 1000 ℃ at the speed of 1.5 ℃/min, and preserving heat for 3 h; finally, the temperature is reduced to the room temperature at 5 ℃/min.

The length of the porous ceramic substrate is 20mm, the width of the porous ceramic substrate is 10mm, and the thickness of the porous ceramic substrate is 2 mm.

In-situ growth nanometer In based on porous ceramic electrode substrate₂O₃NO of₂A method of making a sensor, the method comprising:

① sputtering a Ni film with a thickness of 10nm and an Au film with a thickness of 50nm on the surface of the substrate covering the interdigital electrode mask plate by a plasma sputtering instrument by using a non-metallic mineral material porous ceramic electrode as the substrate through a direct current sputtering method;

② 0.35g of InCl₃·4H₂Dissolving O in 36mL of deionized water, and stirring at room temperature for 10 min; then adding 0.25mL of oleic acid, and stirring for 10min at room temperature; then adding 1g of urea, stirring for 10min, and finally pouring the mixed solution into a 100mL polytetrafluoroethylene reaction kettle;

③ vertically placing the non-metallic mineral porous ceramic electrode substrate obtained in step ① in a polytetrafluoroethylene reaction kettle, sealing, placing in a box-type resistance furnace for heat treatment, heating to 80 ℃ at a speed of 10 ℃/min, and keeping the temperature for 12 h;

④ after the reaction, taking out the electrode substrate, washing the electrode substrate with deionized water, drying at 80 deg.C for 1h, placing In a tubular resistance furnace, heating to 400 deg.C at 2 deg.C/min, maintaining the temperature for 1h, naturally cooling to room temperature, taking out the electrode substrate, placing In a gas sensitive test system, contacting the test probe with the interdigital electrode to obtain In₂O₃Room temperature NO with nano material as sensitive layer₂A gas sensor.

The gas sensitive test method was carried out using (GB-T15653-1995).

Upon examination, In-based films prepared In this example₂O₃The gas sensor of the nano material is used for detecting 0.1-1 ppm NO at the room temperature of 25 DEG C₂Has good gas-sensitive property.

Claims (5)

1. In-situ growth nanometer In based on non-metallic mineral electrode substrate surface₂O₃Room temperature NO of₂A sensor, characterized by: the non-metal mineral electrode substrate is a non-metal mineral porous ceramic electrode substrate, and the NO is₂The sensor is In-situ grown on the surface of a non-metal mineral porous ceramic electrode substrate₂O₃Obtaining a nano material; wherein, said In₂O₃The nanometer material presents a rod-shaped structure and uniformly and densely grows on the surface of the electrode substrate, and the rod-shaped structure is formed by mutually stacking nanometer particles; the nano-particles are In₂O₃A cubic phase crystal structure; the diameter of the rod-shaped structure is 120-200 nm, the length of the rod-shaped structure is 0.5-1 mu m, and the diameter of the nano-particles is 10-30 nm.

2. The In-situ growth of nano-In on the surface of the nonmetallic mineral electrode-based substrate according to claim 1₂O₃Room temperature NO of₂A sensor, characterized by: the nonmetal mineral porous ceramic electrode substrate is made of diatomite or kaolin containing aluminosilicate components, and is subjected to porous treatment by adopting a pore-forming agent pore-forming method, wherein the pore-forming agent is spherical graphite or PMMA microspheres, the average diameter of the pore-forming agent is 10-70 mu m, the addition ratio is 15-50 wt%, and the nonmetal mineral porous ceramic electrode substrate is formed by adopting a mould pressing sintering method, and the sintering temperature is 1000-1200 ℃.

3. The In-situ growth of nano-In on the surface of the nonmetallic mineral electrode-based substrate according to claim 1₂O₃Room temperature NO of₂A sensor, characterized by: the length of the non-metal mineral porous ceramic electrode substrate is 15-20 mm, the width is 5-10 mm, and the thickness is 1-2 mm.

4. Room temperature NO according to claim 1₂The preparation method of the sensor is characterized by comprising the following steps: the method comprises the following process steps:

①, taking a non-metallic mineral porous ceramic electrode as a substrate, sputtering a layer of Ni film with the thickness of 10-20 nm on the surface of the electrode substrate covering the interdigital electrode mask plate by a plasma sputtering instrument through a direct current sputtering method, and then sputtering a layer of Au film with the thickness of 50-100 nm;

② mixing InCl₃·4H₂Dissolving O in deionized water, stirring uniformly at room temperature, then adding 0.1-0.5 mL of oleic acid, stirring uniformly at room temperature, then adding urea, stirring for 5-15 min, and then transferring to a polytetrafluoroethylene reaction kettle, wherein InCl₃·4H₂O concentration of 0.03-0.04 mol/L, In³⁺The molar ratio of the ions to the urea is 1: 8-1: 12;

③, vertically placing the non-metallic mineral porous ceramic electrode substrate obtained in the step ① in a polytetrafluoroethylene reaction kettle, sealing the reaction kettle, placing the reaction kettle in a box-type resistance furnace for heat treatment, heating to 60-100 ℃ at a speed of 10 ℃/min, and preserving heat for 6-14 hours;

④ after the reaction, taking out the electrode substrate, washing the electrode substrate with deionized water, drying at 80 ℃ for 1h, placing the electrode substrate In a tubular resistance furnace, heating to 300-500 ℃ at a speed of 2 ℃/min, keeping the temperature for 1-2 h, naturally cooling to room temperature, taking out the electrode substrate, placing the electrode substrate In a gas-sensitive test system, and contacting a test probe with the interdigital electrode to obtain the In₂O₃Room temperature NO with nano material as sensitive layer₂A gas sensor.

5. The manufacturing method according to claim 4, wherein the interdigital electrode mask plate in the step ① has an interdigital width of 0.2-0.5 mm and an interdigital pitch of 0.2-0.5 mm.

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